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Showing entries 1 to 6

Displaying posts with tag: disk (reset)

Understanding B+tree Indexes and how they Impact Performance
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posted by Ovais Tariq on Thu 14 Jul 2011 10:03 UTC
Tags:
(edit) mysql, indexing, performance, indexes, speed, key, disk, children, integer, B+Tree, binary search tree, branching factor, data structure, disk access, height, index value, inner working, leaf node, linked list, lookup, node, page size, range lookup, sequential scan, shallow
Indexes are a very important part of databases and are used frequently to speed up access to particular data item or items. So before working with indexes, it is important to understand how indexes work behind the scene and what is the data structure that is used to store these indexes, because unless you understand the inner working of an index, you will never be able to fully harness its power.
On LVM: How to setup Volume Groups and Logical Volumes.
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posted by Ovais Tariq on Sat 28 May 2011 11:46 UTC
Tags:
(edit) mysql, debian, Backup, ubuntu, lvm, DBA, partition, fdisk, lvs, filesystem, lvm2, disk, snapshot, ext4, mount, boot, create volume, df, fstab, logical volume, logical volume management, lvcreate, mkdir, partition table, physical volume, pvcreate, system startup, terminologies, vgcreate, vgs, volume group
LVM (Logical Volume Management) is a very important tool to have in the toolkit of a MySQL DBA. It allows you to create and extend logical volumes on the fly. This allows me to, say, add another disk and extend a partition effortlessly. The other very important feature is the ability to take snapshots, that you can then use for backups. All in all its a must have tool. Hence, this guide will allow you to understand various terminologies associated with LVM, together with setting up LVM volumes and in a later part will also show you how to extend...
mount: /dev/sdb1 already mounted or /mysql busy
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posted by Alex Lurthu on Thu 10 Jun 2010 06:56 UTC
Tags:
(edit) mysql, Hardware, troubleshooting, disk, mount

We added a 500GB 7.2K SATA/300 Hitachi Deskstar E7K500 16MB disk to one of our dev servers and partitioned using fdisk and formatted the partition with etx3. When we tried mounting the same, we got the following error :

[root@xyz user]# mount -t ext3  /dev/sdb1 /mysql
mount: /dev/sdb1 already mounted or /mysql busy

lsof didn’t provide any open files that might be linked to this problem or there was any “famd” running. Finally doing the following steps to remove the logical devices from the device-mapper driver helped us fix the problem.

[root@xyz user]# dmsetup ls
ddf1_44656c6c202020201028001510281f033832b7a2f6678dab   (253, 0)
ddf1_44656c6c202020201028001510281f033832b7a2f6678dab1  (253, 1)

[root@xyz user]# dmsetup remove




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Kontrollkit – new backup script is partition space aware
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posted by Matt Reid on Tue 30 Mar 2010 20:55 UTC
Tags:
(edit) mysql, Linux, Backup, database, performance, Python, unix, Backups, partition, mysql server, Scripting, kontrollbase, disk, kontrollkit, announcement, relational, kontrollsoft
I’ve been wanting to write a backup script for a while now that does the following: reads the partition information for the directory that you are backing up into and computes the used/available/percentage-available space. Then it reads the total data size from the MySQL tables and ensures that you have enough space on disk (for [...]
MySQL Cluster Disk Data Tables
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posted by Andrew Hutchings of team blog MySQL Support Team on Sun 21 Feb 2010 21:20 UTC
Tags:
(edit) mysql, cluster, disk
MySQL Cluster is well known as an in-memory database which can be restrictive (a server typically has a RAM limit) so it may surprise some to learn that you can also store MySQL Cluster data on disk.  Disk Data Tables have been in MySQL Cluster for quite a while, the first GA release with them included was 6.2.  They do have caveats which I will describe here, many of which already have plans to be improved in future versions.

How Disk Data Tables work

A set of UNDO logs and data files can be created which are on every data node in the cluster.  The UNDO logs bring the disk data back to a consistent point so that during node restart the REDO logs can be replayed when a node is started.

Not all data in a disk table is actually stored on disk, the main two things that are not are indexed columns (the entire column is in main memory, not


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mysql and disk space anomoloy
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posted by Alex Lurthu on Mon 29 Dec 2008 06:05 UTC
Tags:
(edit) mysql, disk

Every hour, we saw the diskspace on our root partition go up from 45 %  to 90 % and come back to 45 %. Initially thought mysql was processing some temp tables and in the next hour we kept watching the temp location. In terms of files / diskspace usage using “du / ls” nothing changed. But lsof provided an interesting output.

Output 1 :

mysqld    31719   mysql    6u   REG                8,1          0   149240 /var/tmp/ibOLLuRa (deleted)
mysqld    31719   mysql    7u   REG                8,1        102   149243 /var/tmp/ibNuSvI9 (deleted)
mysqld    31719   mysql    8u   REG                8,1          0   149245 /var/tmp/ibqq2wz8 (deleted)
mysqld    31719   mysql    9u   REG               


  [Read more...]
Showing entries 1 to 6

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